In various dental surgical procedures, jaw surgery in general and work with oral implants, it is a common practice to insert a cylindrical implant into a bore or implant cavity provided for this purpose in the jawbone of a patient.
A number of problems have been encountered in connection with the drilling of such cavities and indeed, these problems can be so severe that in some cases the use of implant techniques must be discarded since there are no anatomical conditions in which a satisfactory attachment of the implant can be guaranteed. Such cases include, for example, the lack of sufficient bone substance for an implant cavity.
However, even when there is sufficient bone substance for an implant cavity, problems have been encountered in the past in forming the implant cavity with a sufficient degree of precision, parallelism and spacing, especially where a number of implant cavities are required in a certain region of a jawbone.
Usually such bores are formed in a freehand manner in the jawbones. Of course, this can readily result in defective bores. There is a danger that the bore will be at such an inclination or position that the spongiosa or cortical bone will be excessively damaged in the transverse direction. Such damage may result in jaw resorption. The importance of the transverse dimension is that with implantation, one should ensure a thickness of about 1 mm of spongiosa between an implant and the laminar externa and interna of the respective jaw structure to ensure a sufficient blood supply around the implant and hence growth of bone tissue around the implant to anchor it. Failure to maintain precision and spacing with respect to this dimension may cause of a variety of problems. Bone grafting or other procedures may be required to assure proper orientation or positioning of the implant cavity in the bone.
When the implant is subjected to loading and when the implants are not exactly parallel to one another or to the teeth, that there is an element of transverse pressure transmission to the implant. This provides a pressure effect on one side of the implant and a tension effect on the opposite side. Both effects increase, over extended periods, the bone resorption effect and give rise to a funnel-shaped bone resorption pattern which can produce secondary infections around the implant which may lead to failure of the implant.
The prior art is replete with references to the problems inherent in providing an cavity in which a dental implant can satisfactorily be installed that will support a single tooth or, with other implants, plural teeth. As suggested, and as will be discussed in more detail, the problems inherent in drilling or cutting cavities to receive dental implants is exacerbated where plural adjacent implants must be installed.
In order to fabricate a dental prosthetic, such as a crown, inlay, bridge etc., a negative impression of a patient's mouth is taken using an impression material, and a reproduction of the impression is made as a model in the dental laboratory.
A technique has been described by Lauks in U.S. Pat. No. 4,998,881 in which a model is made from conventional impressions or negative molds of a person's teeth and gums. During the pouring and casting of the dental casting material in the negative mold, a longitudinal, tapered pin or rod is embedded in the casting material The pin or rod extends longitudinally through the base of the model beneath the teeth impressions of the model, with the pin or rod being positioned so that the longitudinal axis of the pin or rod lies in general parallel alignment with the line of the teeth in the negative mold. The pin or rod must extend along a longitudinal direction through the model that is being made such that the pin or rod extends beneath the teeth in the model. In this method, after the model has been poured and the casting material has set into a hard cast model, the model is removed from the negative mold. The longitudinal pin or rod is withdrawn and removed from the model, and the desired dies are sectioned from the model, i.e., the model is cut into the desired sections to isolate one or more teeth for which a dental prosthesis is to be made. These sections can be reassembled on the pin or rod to recreate the precise, true relationship of the teeth in the dental model prior to the cutting of the model into sections. This allows the prosthetic device being constructed to be formed to not only fit exactly the remnant of the tooth that has been prepared by the dentist but to also precisely conform with adjacent teeth of the patient's mouth. Thus, in a very, very general sense, the use of a series of individual generally cylindrical or modified cylindrical tooth emulations in the preparation of dental prostheses is known.
In the Lauks method the end of the pin or rod that extend from the dental model is made to be attached to and detached from an articulation system that allows the dental prosthetic device that is being constructed to be formed to conform and match the teeth in the opposite row of teeth for proper occlusion of the teeth as the patient bites and chews. The Lauks articulation system comprises a flex member which can be made of plastic, rubber or a spring member such as a coiled spring. The respective models are attached by way of the pin or rod of each model to opposite ends of the flex member. The models can then be moved in lateral or protrusive movements and back to centric occlusion to check proper mating of the prosthetic device with the tooth and teeth that it occludes during biting and chewing. In this step, the spacing and size of the teeth are, to some extent, taken into consideration; however, there remains the problem of providing parallel cavities in which to install the implants for supporting the prosthetic teeth.
The affixation of a tooth prosthesis to a patient is traditionally, in older procedures, achieved by basically a three stage process. In these traditional procedures, the gums are allowed to heal following extraction or loss of natural teeth. After the initial healing, surgeon cuts down through the gingiva to expose the underlying bone. The surgeon then burrs into the bone to insert a dental implant. The dental implant itself can be either press-fitted down into a hole drilled in the bone or it can be screwed down into that hole. A cover is then placed over the screw hole in the center of the anti-rotational coupling and the overlying gingiva tissue is then closed back over or around the implant. Healing is then permitted. Following this first stage healing, the surgeon cuts away the gingiva surrounding the head of the dental implant, removes the cover and then inserts a second stage healing cap onto the head of the dental implant. After a period of time, the stitches are removed and the restorative doctor and dental technician then begin the third stage: creating a prosthesis that is permanently secured to the dental implant. The healing cap is removed and a transfer impression is taken of the jaw containing the implant. To preserve the location of the opening to the dental implant when creating the stone model from the impression, an impression post is coupled to the head of the implant.
The healing cap is then reinserted into the dental implant in the patient's mouth to continue to preserve the cavity in the gingiva until either the temporary and, eventually, the permanent crown is in place. A stone model is created from the transfer impression and the stone model becomes the model from which the restorative doctor and the dental technician create the prosthesis. Ultimately, the prosthesis is installed on the implant using screws, abutments, adhesive, or other attachment or fastening means.
More modern approaches permit taking an impression earlier, e.g. at the time of extraction or the immediate installation of implants. One of the more modern approaches is described in U.S. Pat. No. 5,312,254, issued May 17, 1994 to Dr. Joel L. Rosenlicht. According to this procedure, an implant is mounted in a patient's mouth for prosthodontic restoration, in a manner requiring a minimal handling of parts, reducing patient visits, with improved results, and significantly reducing the elapsed time from the beginning to the conclusion of the prosthodontic procedure. Dr. Rosenlicht discovered that taking an impression at the first sitting of the patient, immediately following the insertion of the implants into the bone, has no significant pathological morbidity or other detrimental effects and that the location of implants, utilized in a two-stage process, remain essentially constant so that initial impressions are as accurate as impressions made following a several month healing period.
According to this more modern approach, a sterile package is provided that includes an implant having secured thereto a transfer pin which also serves as an insertion tool. The package including a carrier has a unique interior wall surface engaging the combination insertion tool/transfer pin, so that the implant may be started into the bone in a sterile manner, using the components shipped as a sterile set. According to this method, an impression is taken as soon as the carrier is removed from the combined insertion tool/transfer pin, after which the transfer pin is removed and a healing screw is inserted to the outer end of the implant in order to keep it clean for ultimate mating with an abutment which will mount the prosthesis. By taking the impression immediately--which allows the laboratory work to begin immediately for forming of the model of the mouth and the ultimate prosthesis and/or abutment structure while the initial healing takes place. This method avoids having to enter the gum tissue more than twice, since the second invasion is to remove the healing screw and mount the ultimate abutments and/or prosthesis. The procedure avoids the necessity for handling a transfer pin and concomitant screw at a second sitting, after healing has taken place. Thus, fewer steps are required, as fewer parts are handled. This significantly reduces the risk of infection as well as significantly reducing the risk of losing small parts--possibly in a patient. Another great advantage of the Rosenlicht method is that the transfer pin is always firmly and tightly secured to the implant at the factory, under ideal conditions, rather than being attached to the implant in the surgical field. A concomitant advantage is that providing a new insertion pin for each implant avoids the possibility of poor fit to the implant due to scratches in the mating surface of the transfer pin or inter-lodging debris. The invention also eliminates the use of two parts: the insertion tool and the screw used to hold the original transfer pin.
Systems for mating dental prosthetic components together are, as illustrated, well known. For example, it is now common practice to fit an abutment that forms a recess over the head of an implant. Commonly, a hex head on the implant and a mating recess on the abutment assist in vertical alignment of the prosthesis components. Ball and socket keyed components are referred to in U.S. Pat. Nos. 5,417,570 and 3,787,975 to Max Zuest. However, none of the know prior art addresses the use of articulated tooth emulations to assure spacing and alignment of implants.
The dental prosthesis art generally and the dental implant art has experienced almost explosive activity in the past decade and have become crowded art. Important progress is made, however. Sometimes, the magnitude of an advance step is not recognized because great changes is structure, materials, etc., are rarely encountered. There remain, nevertheless, very serious problems in the art, not the least of which are the problems associated with drilling holes in proper inclination to receive dental implants upon which prosthetic teeth can be mounted. Even more serious is the problem of drilling plural holes in the jaw bone at proper spacing and in proper inclination for mounting plural implants adjacent each other in the patient's jaw bone. It is to this problem that the present invention is directed.
Prior to this invention most method most procedures have involved the taking of an impression and the making mounted models so that a surgical guide stent or guide may be made. This step, making of a guide on the model, is usually non-sterile, costly, and has numerous limitations in use. It can only be used for the individual patient for whom it is made, it is difficult to alter as different anatomic problems are incurred and may be bulky.
A feature of this invention is the provision of a quick, highly accurate, and inexpensive method and means for assuring proper spacing and orientation of holes to be drilled in a patient's jaw bone to receive implants.